1. Field of the Invention
This invention relates to a beam recording apparatus effecting the recording by a plurality of beams in which a plurality of beams modulated with modulation signals are projected upon a recording medium to thereby record information on the recording medium.
2. Description of the Prior Art
In the conventional recording apparatus for recording information on a recording medium, the recording medium is scanned with a single beam to effect the recording and therefore, when printing is to be effected at high speed, it is necessary to increase the transfer speed of information signals for modulating the beam.
It is also necessary to speed up the main scanning and therefore, when a rotatable polygonal mirror is used for the main scanning, the number of revolutions thereof must sometimes be as great as several tens of thousands of rpm (revolutions per minute) and necessarily, there is a structural limit in making the apparatus into a high speed recording apparatus.
If the light beams from a plurality of light sources arranged in a row are deflected by a rotatable polygonal mirror to scan a recording medium, it will be possible to obtain a high speed recording apparatus, but if the beams are arranged in a direction perpendicular to the auxiliary scanning direction of the recording medium, there is a disadvantage that the interval between adjacent beams cannot be narrowed to less than a predetermined distance.
To eliminate such a disadvantage, I proposed in Japanese Patent Laid-open Publication No. 38130/1979 a scanning device in which the recording medium is irradiated with a plurality of beams so that the beams are not perpendicular to the auxiliary scanning direction of the recording medium.
However, if the recording medium is scanned with the beams being so inclined, the times during which the respective beams cross the recording medium differ and this leads to complicated control of the recording and difficulty with which the recording is effected at an accurate position.
Also, if information recording is effected by the beams so inclined to in the scanning direction, the scanning pitch in the auxiliary scanning direction of the recording medium by the beams is determined by the arrangement of the plural beams and is thus invariable even if the main scanning speed and the auxiliary scanning speed are varied. Therefore, where a single beam is used, the auxiliary scanning density can be doubled by doubling the main scanning speed, for example, and the recording of high density and high quality can be accomplished by the same apparatus, but where a plurality of beams are used, this cannot be accomplished unless a complicated interlace system is adopted, and it is difficult to effect the recording of high density and high quality by the same apparatus with the scanning pitch in the auxiliary scanning direction being variable.